A First Study of the Kinetics of Metal Ion Adsorption at Solid/Liquid Interface Using Evanescent Wave-Based Optical Microfiber

Although the use of chelating agent (CA)-functionalized optical microfiber (OM) for heavy metal ion sensing has been receiving tremendous research interest, a thorough study of the kinetics and adsorption of metal ions process which occurs at the solid/liquid interface has yet to be investigated. Kinetics and adsorption studies of metal ions, M
²⁺
(i.e. Cd
²⁺
, Pb
²⁺
, and Zn
²⁺
) were carried out using CA-functionalized OM. The optically measured metal adsorption efficiency is interrelated to the properties of the chelating ligand, metal ion, and the molecular structure of the CA-M
²⁺
complex that include the coordination number, bond length, and bond angle parameters. The kinetics adsorption chemistry of M
²⁺
onto the CA-functionalized OM is well-fitted to the pseudo-first-order kinetic model. Moreover, this work also investigated the effects of the resultant optical evanescent field strength and the CA-M
²⁺
structure towards the adsorption efficiency of OM with reduced tapered waist diameter. To the best of our knowledge, this is the first reported study to find this correlation in the metal adsorption efficiency at solid phase using an OM. The denouement of this study unveils a new physical chemistry insight of metal ion adsorption at the solid/liquid interface.